Liver Enzyme Alteration Prof. Dr. Orhan Tarçın Gastroenteroloji Bölümü

Biochemical markers of liver damage Isolated alterations in healthy patients Guidelines ? Classify: hepatocellular vs. cholestatic Initial investigation

Liver enzyme levels Aim of this presentation: Defines the laboratory diagnosis for abnormal liver enzyme. Providing how to in the interprate the liver enzyme alterations.

***Edoardo G. Giannini, MD

Normal Ranges: How to apply reference ranges? Performance characteristics (reproducibility, bias, total error). Definition: a value exceeding the upper reference limit is abnormal. Low levels has no significance – except: serum albumin. Use your own laboratory ranges… Remember there are patients with subclinical liver disease included. 2.5% of “normal” patients have “abnormal” - AST or ALT Some patients with chronic hepatitis C- 16%, non-alcoholic fatty liver-13% have normal laboratory measurement with abnormal histological findings. Age and sex limits Activity- exercise: ↑ALT & ↑AST Hospital patients- diet? And ↓exercise restriction- ↓

Fig. 1: Schematic representation of an approach to liver enzyme alteration. Specific modalities of enzyme alteration (how) and their relation with peculiar characteristics of the patient and locality (where and when) should be thoroughly assessed before the definitive diagnostic work-up is begun.

Where, When and How Always ask questions…Traveling…Ethnicity Where? Who is your patient? – Example: Bayamón, P.R. – 50%- ↑ALT (genetics?) – Wales- 60% - ↑ AST (due to ischemic or toxic liver disease). – Far East- orofecal transmittable hepatitis viruses (60%) are the major causes of sporadic acute and fulminant hepatitis.⁵ – Primary Biliary Cirrhosis 2% in Australia;.424 per 100,000 in Asia. – Homozygosity for the C282Y mutation in the HFE gene can be found in about 5/1000 people of Northern European descent but.0001/100 people of African American ethnicity.

When? Timing in relation to age of the patient – Example: Wilson’s disease – early in life Comorbid conditions should be explore Ingestion of medications. – Date it started with relation to alterations. – Almost any medication can liver enzymes. – Herbal remedies are overlooked. – Over the counter meds..

How? First piece of evidence: Pattern. – Disease: Common causes have typical patterns… – Careful examination- Predominant pattern- (hepatocellular vs. cholestatic) Magnitude of alteration ( 10 times); mild, moderate or marked. Rate of change (increase or decrease over time) The nature of the course of alteration (mild fluctuations vs. progressive)

Serum aminotransferace levels in various liver disease

Hepatocellular predominant and cholestatic predominant Fundamental to narrowing down the differential diagnosis. Certain liver diseases may display a mixed biochemical picture- – ↑AST and ↑ALT with mild abnormalities of alkaline phosphatase (ALP) and gamma- glutamyl transpeptidase (GGT) levels-

Hepatocellular predominant AST and ALT increased: – are enzymes that catalyze the transfer of α-amino groups from aspartate and alanine to the α-keto group of ketoglutaric acid to generate oxalacetic and pyruvic acids respectively, which are important contributors to the citric acid cycle. Both enzymes require pyridoxal-5’-phosphate (vitamin B6) in order to carry out this reaction, although the effect of pyridoxal-5’-phosphate deficiency is greater on ALT activity than on that of AST. This has clinical relevance in patients with alcoholic liver disease, in whom pyridoxal-5’-phosphate deficiency may decrease ALT serum activity and contribute to the increase in the AST/ALT ratio that is observed in these patients.

Hepatocellular predominance Both aminotransferases are highly concentrated in the liver. AST is also diffusely represented in the heart, skeletal muscle, kidneys, brain and red blood cells, and ALT has low concentrations in skeletal muscle and kidney. An increase in ALT serum levels is, therefore, more specific for liver damage

Marked and moderate aminotransferace increase > 10 times the upper reference limit: acute hepatic injury. – Data suggest that the most sensitive and specific aminotransferase threshold is within the moderate range (5-10 at 200 IU/L for AST and 300 IU/L for ALT).

Schematic representation of the rate of change of aminotransferace and bilirubin levels in a patient with acute ischemic hepatitis (green and yellow) and acute viral hepatitis.(blue and orange) figure 3

A minimal or mild increase in aminotransferase level is the most common biochemical alteration encountered in everyday clinical practice. Mild increase in aminotransferase levels

Nonalcoholic fatty liver disease is the most common cause of mild alteration of liver enzyme levels in the western world, and, according to the National Health and Nutritional Survey, point-prevalence is about 23% among American adults. The biochemical picture includes mildly raised aminotransferase levels, and GGT levels can be elevated up to 3 times the upper reference value in nearly half of patients in the absence of ethanol consumption. As with chronic viral hepatitis, an AST/ALT ratio greater than 1, which is observed in 61% of patients with advanced fibrosis and 24% of patients with no or initial fibrosis, is highly suggestive of advanced liver disease

Mild increase in aminotransferase Suspicion of nonalcoholic fatty liver disease is increased by the presence of conditions linked to the metabolic syndrome and insulin resistance (increased body mass index, diabetes, hyperlipemia, hypertension), although the disease may occur in patients without these associated factors.

All patients presenting with mild increases in aminotransferase levels should be questioned about risk factors for hepatitis B or C infection (intravenous drug use, exposure to nonsterile needles or sexual exposure to an infected person). However, since these 2 diseases have a high prevalence worldwide and infected people may lack or underreport specific risk factors for infection, testing for HCV antibodies and hepatitis B surface antigens is advisable for all patients presenting with a mild increase in aminotransferase levels. If the patient tests positive for HCV antibodies, then qualitative HCV RNA testing should follow.

Cholestatic predominance Presentation of liver injury with a prevalent cholestatic pattern is less frequently encountered in clinical practice than the pattern of hepatocellular damage. ALP and bilirubin levels are routinely assessed, and the level of GGT is often measured as an additional aid toward diagnosis in particular situations because of its high sensitivity but low specificity. (Dosage of AlP isoenzymes is a more complicated technique and expensive, so GGT is preferred)

Albumin and prothrombin time assessment: Are we really testing liver function? Determining serum albumin levels and assessing prothrombin time are often considered “tests of liver function.” …because hepatic synthesis of albumin tends to decrease in end-stage liver disease Increase in prothrombin time depends on the decreased synthesis of liver-derived coagulation factors., In fact, Albumin is produced by hepatocytes, and prothrombin time depends on the activity of clotting factors I, II, V, VII and X, which are produced in the liver. Neither test is specific for liver disease, since albumin serum levels may decrease in patients with nephrotic syndrome, malabsorption or protein-losing enteropathy, or malnutrition, andprothrombin time may be prolonged by warfarin treatment, deficiency in vitamin K (which is needed to activate clotting factors II, VII and X) and consumptive coagulopathy.

Conclusions Alterations in liver enzyme levels are one of the most common problems encountered in everyday clinical practice. Finding the way through the multiple diagnostic pathways can challenge even the experienced clinician. Knowledge of the pathophysiology of liver enzymes is an essential guide to understanding their alteration. The pattern of enzyme abnormality, interpreted in the context of the patient’s characteristics, can aid in directing the subsequent diagnostic work-up. Awareness of the prevalence of determined liver disease in specific populations and of possible hepatic involvement during systemic illnesses or drug therapies may help the clinician identify the cause of alterations efficiently.